1. The Field of the Invention
This invention relates to digital computing equipment. More particularly, the present invention relates to devices used to interconnect computing equipment in a network configuration.
2. Background Information
The proliferation of computers has made great computing power available to large numbers of users. The flexibility and capabilities of personal computers is greatly enhanced when the computers are interconnected to each other. When a plurality of computers are interconnected to share information, it is generally referred to as a network. Local Area Networks (LANs) are those networks which connect computers over a relatively small geographic areas and Wide Area Networks (WANs) are those networks which connect computers over a relatively large geographic area. With millions of computers being connected to each other as part of various networks, efficient use of computing resources becomes very important.
In order to allow a computer to be connected to a network, the computer must be provided with the appropriate network hardware. Such hardware is referred to as a network adaptor card. A network adaptor card may adhere to many different network standards, such as one of the popular Ethernet network standards or one of the Token ring network standards. A network adaptor card also adheres to one of the many standards which allow the network adaptor card to communicate with the computing device. The standards which allow the network adaptor card to communicate with the computing device include, for example, the PCI standard, the ISA standard, the PCMCIA and CARDBUS standards, the various IEEE RS standards (e.g. RS-232), as well as other standards. All of these standards are examples of standards which are well-known in the industry but the recitation of these standards is not intended to be a comprehensive list of those standards which are applicable to the present invention.
Represented in FIG. 1 is a diagram showing the general arrangement of a host computer, a network adaptor card, and a connection to the media conveying a network signal used in the case of the Ethernet network standard. It is to be understood that the arrangement represented in FIG. 1 is merely exemplary and not limiting of the applications of the present invention or is indicative of any particular network arrangement.
As represented in FIG. 1, a network adaptor card 10 resides in a host computer 12. Network adapter cards, such as network adaptor card 10, used in connection with personal computers, such as host computer 10, typically contain a transceiver 14 which interfaces between the media access controller (MAC) 16 on the network card 10 and the physical network media 18 (e.g. the media carrying the network signals (twisted pair cable, coaxial cable, or fiber optic cable)). The transceiver 14 is also sometimes referred to as a Medium Attachment Unit. In the example of FIG. 1, when implementing the Ethernet network standard the transceiver 14 performs the task of transmitting the data frames onto the cable and receiving data frames from it. The transceiver 14 also monitors the signal level on the medium, acts as an electrical isolator between the network adaptor card 10 and the network media 18, and detects network collision and other error conditions, all as known in the industry. The transceiver 14 can either be external to, or on-board, the network adaptor card 10. Other components which are included on the network adaptor card 10 are represented at 22.
Besides functioning to convert between the signals of the MAC 16 and the signals that appear on the network media 18, the transceiver 14 is involved in establishing the network connection in the first place. When the host computer 12 initializes the network card 10, the transceiver 14 continuously monitors the network media 18 while typically sending out its own broadcast packets until there is a response from the network and a connection established. Some transceivers 14 that support more than one type of connection call the process of determining which types of signals must be used on the network “autonegotiation.” It is to be understood that the functions carried out by the network adaptor card 10 can be integral with other components of the host computer 12 or other type of computing device.
The advent of PCMCIA cards and CardBus cards, collectively known as PC Cards, has brought networking to the portable computer user. Such portable computers are battery powered devices which are small, easily carried devices often the size of a notebook or smaller. PC cards are compact hardware devices having dimensions of about 2.1 inches by about 3.4 inches with a thickness of only 3.5 mm, 5 mm, 10.5 mm or some other dimensions allowed by the promulgated PCMCIA standard. The PC Card typically slides into a socket provided on the housing of the computer to allow easy replacement of one PC Card with another PC Card. Increasingly, users of desktop computers, as well as other electronic devices, are also using such PC Cards to add hardware devices to their computing devices.
It is common to add a network adaptor card to a portable computer as a PC Card. Some of these PC Cards also contain a modem and are known as network/modem combination, or “combo,” cards. Often the portable computer user is only using the modem portion of the PC Card, or the user simply keeps the PC Card in the host computer even when the PC Card is not connected to any network. Since the network PC Card is installed in the PC Card slot on the computer, the PC Card still gets initialized by the host computer, and the transceiver (see 14 at FIG. 1) on the card continuously attempts to find a network connection, even if no connection to network media is present. The amount of power used by the transceiver is great enough to unsatisfactorily reduce the battery life of portable computers when being powered from the internal battery. In addition, because network and modem components on a combination network/modem card are in such close proximity, the constant attempts of the transceiver to find a network connection creates electrical noise that can adversely interfere and affect modem performance since the circuit board in the PC Card contains the components for both the modem and the network adaptor.
To reduce undesirable power consumption and electrical noise when the transceiver is not needed, most transceivers can enter a low-power mode. However, the circuitry needed to establish a network connection is disabled in a transceiver when the transceiver is in the low-power mode. While it has been suggested that it is possible to put the transceiver into the low-power mode and periodically give it full power to check for a cable being connected to the network adaptor card, this suggestion is impractical since in order to significantly reduce power consumption and minimize electrical noise, these full power checks are so infrequent that it results in an unacceptable delay in connecting to a network when a cable carrying active network signal is actually attached to the network adaptor card. Additionally, the software overhead required of the host computer for such an ongoing operation would hurt the performance of all other tasks the host computer is running. Moreover, merely mechanically detecting when a network cable is connected to the network adaptor card also provides unsatisfactory performance since there is no guarantee that the other end of the cable is actually connected to a network hub, switch, or router and that the cable is carrying an active network signal.
In view of the foregoing, it would be an advance in the art to provide a system and method for reducing the power consumed by a network adaptor card when the network adaptor is not actively connected to a network.